Excitation of resonance transitions in argon atoms by electron impact in the distorted-wave Born approximation: role of the imaginary part of the optical potential

The total and differential cross sections for the excitation of the 3p -1 4s 1 P state in argon and also the correlation parameters lambda and chi have been calculated using the distorted-wave Born approximation. Different variants of the distorting potential are used. It is shown that the inclusion of the imaginary part of the optical potential in a semiphenomenological form allows one to improve the agreement between the calculated total and differential cross sections and experiment.